By ANNA M. TINSLEY FORT WORTH -- A former city employee has filed a whistle-blower lawsuit alleging that she was wrongly fired after reporting to authorities that millions of dollars in developer fees and checks were not collected or deposited.Catherine Davidson contends that city workers didn't deposit at least 17 checks from developers, totaling about $500,000, and that they didn't collect about $2.4 million in fees "in order to provide special treatment for certain developers such as Hillwood Development Company," according to the lawsuit, filed Thursday afternoon in Wise County's 271st District Court."I was fired by the city of Fort Worth for reporting illegal activity that was costing the city hundreds of thousands of dollars and maybe more," Davidson said in a statement.